This disclosure relates to xerographic or electrostatographic printing machines, and more particularly to a robust apparatus and method of grounding an electrically conductive drum photoreceptor assembly in such a printing machine. The phrase printing machine includes both printing and copying devices.
As is well known, the electrically conductive photoreceptor in an electrophotographic or xerographic printing machine requires grounding for proper operation. One conventional grounding apparatus and method employs a metal strip mechanically attached to one of the non-metallic flanges that cap the ends of the electrically conductive photoreceptor. One end of the metal strip contacts the inside of the electrically conductive photoreceptor while the other end of the metal strip contacts the center metal shaft which rotates the photoreceptor, thus completing the grounding circuit. Any deformation of the metal strip during assembly, however, can result in loss of ground, either permanently or intermittently. Repair of the metal strip within the photoreceptor is difficult since the end flanges are glued in.
Examples of prior efforts at grounding the conductive photoreceptor include U.S. Pat. No. 5,537,189 entitled “Printing apparatus which grounds photoreceptor independently of CRU” that discloses an electrostatographic printing apparatus having (a) a detachable imaging module including a housing and a photosensitive member, wherein the photosensitive member is partially enclosed within the housing, and wherein the photosensitive member has an outer surface which includes an electrically conductive portion; (b) an electrically grounded component free of attachment to the module; and (c) an electrically conductive part, free of attachment to the module, in contact with both the grounded component and the conductive portion on the outer surface of the photosensitive member, thereby establishing grounding of the photosensitive member, and wherein upon removal of the imaging module the part remains in contact with the grounded component and upon insertion of a new detachable imaging module which has a new photosensitive member having an outer surface that includes an electrically conductive portion, the part contacts the electrically conductive portion on the outer surface of the new photosensitive member, thereby establishing grounding of the new photosensitive member.
U.S. Pat. No. 5,815,773 entitled “Composite photoreceptor flange” discloses an end flange capable of translating a rotational force from an outside source to a hollow cylindrical member is disclosed. The end flange is made from a composition which includes polycarbonate, polytetrafluorethylene, and glass. The end flange may be used to rotate an electrophotographic imaging member past a charging station, for generation of a uniform electrical potential thereon, and subsequent selective discharging of the imaging member and development of an electrostatic latent image. Most notably, mounting of the end flange to the imaging member does not require the use of an adhesive material. This enables successful recycling of the imaging member, and results in significant cost savings.
U.S. Pat. No. 5,752,136 entitled “Imaging member end flange and end flange assembly” discloses a hollow cylindrical electrostatographic imaging member supporting end flange including a disk shaped member, a supporting hub extending axially from the disk shaped member and a metal disk coaxially secured to the hub, the disk comprising a plurality of rectangular tabs extending radially from the disk in a direction away from an imaginary axis of the hub for engagement with the hollow cylindrical electrostatographic imaging member upon insertion of the hub and disk shaped member into one end of the hollow cylindrical electrostatographic imaging member. When this end flange is inserted into one end of the hollow cylindrical electrostatographic imaging member, the plurality of rectangular tabs extending radially from the disk engage the inner surface of the hollow cylindrical electrostatographic imaging member.
U.S. Pat. No. 7,103,297, entitled “Robust Apparatus and Method of Grounding a Drum Photoreceptor Assembly” discloses a photoreceptor grounding apparatus including (a) a flange including a first portion having a first diameter and a second portion having a second and smaller diameter; (b) a conductive plating formed on said flange presenting a relatively large conductive surface area for contactably assembling against walls of the conductive photoreceptor drum; and (c) an electrical connector for electrically connecting the large conductive surface area of the conductive plating to an electrically conductive drive shaft of the xerographic image producing machine.
Unfortunately, it has been found that electrical connections using such tabs or clips is not always properly made due to corrosion of or damage to the tabs or clips which are, of a necessity, made from a lightweight strip of very flexible and hence easily damaged strip of metal. These tabs or clips in addition only present a relatively small surface area to work with, and damage to them often includes bending. They may also be installed improperly and foreign material such as glue used to secure the drum to the flange may also interfere with this connection.